iMac 12,1 Mid 2011 GPU Replacement - no boot screen help request

[jimbob200521]

So TLDR I bought this iMac a few years ago, replaced the faulty AMD card with an nVidia Quadro K2000M and somehow at the time got High Sierra up and running. Been a good machine for me but I'd like to tinker with OCLP. My issue is since the nVidia card I installed doesn't give me any screen output until the OS initializes and starts loading at which point it works fine. This is largely troublesome b/c I can't use the option key to get a boot selection screen to choose boot device (USB Drive, etc). Basically any functions outside of a loading/loaded OS aren't useable atm.

I'm finally coming here for help b/c I've gone down idk how many rabbit holes trying to fix this. My last attempt was trying to flash a new BIOS on the GPU using this method:

https://forums.macrumors.com/threads/2011-imac-graphics-card-upgrade.1596614/post-28253271

But the installer failed at the very last step working on the MBR (I'd have to run it again to get the exact error wording). It made the new partition and in Boot Selector I can see the new drive as an option to boot from but I'm scared of trying it b/c if it fails/locked up then I have no good way to get back into OSX.

So I suppose I'm asking for input from y'all as to how to proceed from here. I'd love to use OCLP on this machine to at least get a couple versions newer of an OS but every avenue I go down has lead me to a failure for one reason or another. TYIA for any input/help I can get here savin this ol' girl!

 

[Andrey84]

So TLDR I bought this iMac a few years ago, replaced the faulty AMD card with an nVidia Quadro K2000M and somehow at the time got High Sierra up and running. Been a good machine for me but I'd like to tinker with OCLP. My issue is since the nVidia card I installed doesn't give me any screen output until the OS initializes and starts loading at which point it works fine. This is largely troublesome b/c I can't use the option key to get a boot selection screen to choose boot device (USB Drive, etc). Basically any functions outside of a loading/loaded OS aren't useable atm.

I'm finally coming here for help b/c I've gone down idk how many rabbit holes trying to fix this. My last attempt was trying to flash a new BIOS on the GPU using this method:

https://forums.macrumors.com/threads/2011-imac-graphics-card-upgrade.1596614/post-28253271

But the installer failed at the very last step working on the MBR (I'd have to run it again to get the exact error wording). It made the new partition and in Boot Selector I can see the new drive as an option to boot from but I'm scared of trying it b/c if it fails/locked up then I have no good way to get back into OSX.

So I suppose I'm asking for input from y'all as to how to proceed from here. I'd love to use OCLP on this machine to at least get a couple versions newer of an OS but every avenue I go down has lead me to a failure for one reason or another. TYIA for any input/help I can get here savin this ol' girl!

I can see you have a complex question and you're not getting any responses.
Try posting your message (you'll need to change it slightly) here: https://forums.macrumors.com/forums/early-intel-macs.230/

 

[Nguyen Duc Hieu]

So TLDR I bought this iMac a few years ago, replaced the faulty AMD card with an nVidia Quadro K2000M and somehow at the time got High Sierra up and running. Been a good machine for me but I'd like to tinker with OCLP. My issue is since the nVidia card I installed doesn't give me any screen output until the OS initializes and starts loading at which point it works fine. This is largely troublesome b/c I can't use the option key to get a boot selection screen to choose boot device (USB Drive, etc). Basically any functions outside of a loading/loaded OS aren't useable atm.

I'm finally coming here for help b/c I've gone down idk how many rabbit holes trying to fix this. My last attempt was trying to flash a new BIOS on the GPU using this method:

https://forums.macrumors.com/threads/2011-imac-graphics-card-upgrade.1596614/post-28253271

But the installer failed at the very last step working on the MBR (I'd have to run it again to get the exact error wording). It made the new partition and in Boot Selector I can see the new drive as an option to boot from but I'm scared of trying it b/c if it fails/locked up then I have no good way to get back into OSX.

So I suppose I'm asking for input from y'all as to how to proceed from here. I'd love to use OCLP on this machine to at least get a couple versions newer of an OS but every avenue I go down has lead me to a failure for one reason or another. TYIA for any input/help I can get here savin this ol' girl!

1. Plan your things a head.
2. Clone the internal disk to a blank disk as a back-up plan.
3. I advise against the Windows method. Use GRML Linux method. I suppose GRML linux has the basic driver for K2000m and you can do the flash on the same iMac.